The objectives of this project are to investigate the structure and biosynthesis of lipoteichoic acid and the role of lipoteichoic acid in the adherence of Streptococcus sanguis to the host tissues. the following specific aims will be investigated during the proposal period: 1. Determination of lipoteichoic acid structure. The monoglucosyl moiety, instead of diglucosyl moiety, was found to attach to the polyglycerolphosphate backbone. This is different from the lipoteichoic acid of Streptococcus fecalis. The linkage of sugar to the glycerol moiety will be re-examined, and the structure of the lipid moiety will also be determined. 2. Biosynthesis of lipoteichoic acid. We have found recently a new glycerolphosphate donor, phosphatidyl glycerolphosphate, which is believed to be the glycerolphosphate donor for the polyglycerolphosphate backbone synthesis. Phosphatidylglycerol probably serves only as the donor for the terminal glycerolphosphate moiety, and glucosyl monphosphoryl undecaprenol, instead of UDP-glucose, was found to be the direct glucosyl donor. In this project, the de novo synthesis of lipoteichoic acid will be carried out using those donors mentioned above. 3. Adherence of S. sanguis to the host tissues. Lipoteichoic acid was found to be important in the adherence of S. sanguis to glass surfaces. Mutants deficient in lipoteichoic acid or in the ability to adhere to glsss surfaces will be isolated and a correlation will be made between the bacterial lipoteichoic acid content and the adherence to glass surfaces and animal oral tissues.